MIPS: Set `si_code' for SIGFPE signals sent from emulation too

Rework `process_fpemu_return' and move IEEE 754 exception interpretation
there, from `do_fpe'.  Record the cause bits set in FCSR before they are
cleared and pass them through to `process_fpemu_return' so as to set
`si_code' correctly too for SIGFPE signals sent from emulation rather
than those issued by hardware with the FPE processor exception only.

For simplicity `mipsr2_decoder' assumes `*fcr31' has been preinitialised
and only sets it to anything if an FPU instruction has been emulated,
which in turn is the only case SIGFPE can be issued for here.

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9705/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

2 files changed, 9 insertions, 3 deletions

diff --git a/arch/mips/include/asm/fpu_emulator.h b/arch/mips/include/asm/fpu_emulator.h
index 6370c82eb5e1..bfcc5c64b7b0 100644
--- a/arch/mips/include/asm/fpu_emulator.h
+++ b/arch/mips/include/asm/fpu_emulator.h
@@ -66,7 +66,8 @@ extern int do_dsemulret(struct pt_regs *xcp);
 extern int fpu_emulator_cop1Handler(struct pt_regs *xcp,
                                     struct mips_fpu_struct *ctx, int has_fpu,
                                     void *__user *fault_addr);
-int process_fpemu_return(int sig, void __user *fault_addr);
+int process_fpemu_return(int sig, void __user *fault_addr,
+                         unsigned long fcr31);
 int mm_isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn,
                      unsigned long *contpc);
 
diff --git a/arch/mips/include/asm/mips-r2-to-r6-emul.h b/arch/mips/include/asm/mips-r2-to-r6-emul.h
index dd6f1de5b621..4b89f28047f7 100644
--- a/arch/mips/include/asm/mips-r2-to-r6-emul.h
+++ b/arch/mips/include/asm/mips-r2-to-r6-emul.h
@@ -84,11 +84,16 @@ extern void do_trap_or_bp(struct pt_regs *regs, unsigned int code,
 
 #ifndef CONFIG_MIPSR2_TO_R6_EMULATOR
 static int mipsr2_emulation;
-static inline int mipsr2_decoder(struct pt_regs *regs, u32 inst) { return 0; };
+static inline int mipsr2_decoder(struct pt_regs *regs, u32 inst,
+                                 unsigned long *fcr31)
+{
+        return 0;
+};
 #else
 /* MIPS R2 Emulator ON/OFF */
 extern int mipsr2_emulation;
-extern int mipsr2_decoder(struct pt_regs *regs, u32 inst);
+extern int mipsr2_decoder(struct pt_regs *regs, u32 inst,
+                          unsigned long *fcr31);
 #endif /* CONFIG_MIPSR2_TO_R6_EMULATOR */
 
 #define NO_R6EMU        (cpu_has_mips_r6 && !mipsr2_emulation)